During the production of pipes which are to be threaded together for the crude oil and natural gas industry, depending on the load and area of operation and the type of cut thread, the wall thickness of the end area is increased. Customarily, this is done in the fashion where a certain length of the pipe is hot deformed in a deforming press and the wall thickness is increased. The condition of the surface and the dimensional structural condition of the hot deformed pipe end permits a direct cutting of threads in only a few cases so that it is necessary to perform cleaning and the dimensional processing steps. For this purpose, the pipes with the deformed pipe ends are removed from the production line and are put on a cleaning stand. There, a semi-automatic grinding machine removes the rough surface scale. Afterwards the critical areas are improved and the deforming seams are ground off manually with a hand grinding machine. The deforming seams come about during the deforming process, where for instance, two deforming half molds, which work together are used and part of the material flows into the separation seam between the two deforming half molds. In another embodiment, four deforming half molds are employed where two of them work together as a pair. Also known is the use of an undivided housing in combination with a deforming half mold. In the latter case, the circular bead develops during the deforming process in the area of the transition point between the housing and the deforming half mold.
These beads are a problem on a turning machine for the cutting process which occurs later, because the undisturbed flow of shavings at this point is being obstructed. The unbalanced load leads to an increased wear and tear of the cutting tools with the mounting part of the tool holders affected adversely. Even if one were to make allowances for the stresses on the tool machinery, these beads are still a problem because they lead to a radial movement of the pipe to be worked on within the chucked jaws of the turning machine.
The manual cleaning and finishing of a heat deformed pipe is very expensive based on the use of personnel. Also, the surface quality achieved depends on the subjective evaluation of the operating personnel. Furthermore, depending on the outside surface of the deformation at the transition point in the deformed pipe ends can only be partially accommodated during the cleaning. Also, the grinding provides a danger for the highly stressed pipe connection. Depending on the quality of the manual grinding, dangerous grooves can be formed which reduce the endurance strength.
The removal of the scale can be made through the use of a jet stream, as an alternative to grinding. For the cleaning of the inner surfaces of pipes, it is known from (Bleche, Rohre, Profile 32 (1985) 6, Page 303) to utilize a rotatable nozzle head which is connected to a lance and is filled with a gas type carrier medium, customarily air under pressure, and an abrasive, and where at least one inclined blasting nozzle is located in a longitudinal plane in relation to the inner surface of the pipe. In the area of the nozzle head, the air pressure and the abrasive are mixed and are aimed towards the inner surface of the pipe. This device is of little use for the cleaning of the inner surface of the deformed ends because the rotating nozzle heads are large in size and are not usable for smaller inner pipe end diameters. From the viewpoint of weight, it is wasteful because the nozzle heads have to be supported with a device attached to a lance.
A further disadvantage is the fact that the device for the support of the nozzle head cannot be adjusted to the various inner diameters of a hot deformed pipe end. It is furthermore of a disadvantage, be it with the known jet stream applications, or be it in the type of free-pressure jet stream only from one or the other end, or be it in the type of a combination of pressure and vacuum blast, where a vacuum is developed at the end located across, that the abrasive will be distributed all over the entire pipe and subsequently an expensive cleaning procedure is thus required in order to clean the pipe.